| Electronics > Repair |
| OPA150 Stereo AMP issues, only turns on when I physically heat it up w/ a dryer! |
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| N19htmare:
--- Quote from: wraper on August 30, 2020, 02:14:30 am ---Quite likely faulty zener diode. Most likely there is marking on the opposite side of it, from which we can figure out its rated voltage. But you will need to desolder it to see the marking. --- End quote --- it is a either a C12 5T or C12 ST, I can't tell if a 5 or an S. per marking. In case I can't find this exact part? alternatives? The only one I have on hand are 4148ST diodes. I have taken the diode out of the board, is there any way to test it with the meter? should there be any resistance values or anything. a new 4148st diode i have registers 7.75K ohms however when I test the removed diode it registers 750 ohms. does that mean anything? I'm going to try to find all the resistor values and the opamp and just replace everything and see. Wish I could just go down the street and grab a diode but that's not an option for me. |
| N19htmare:
Update: I took out all the resistors and diode. I measured the resistors out of the amp and they corralate their reading with the line markings I checked online, I'm getting new ones anyways. The Diode has a resistance of 750ohm which I'm not sure because the 12C diodes im looking on Mouser do not show that high of resistance value (unless zener resistance is something different). Speaking of which, there are so many 12V diodes that end with with either C12 or 12C... which do I get? Cheap enough to get them all but which do I use? https://www.mouser.com/ProductDetail/Vishay-Semiconductors/BZX55C12-TAP?qs=yIvl1B2wDi6k6fC%252BTXe4cg%3D%3D https://www.mouser.com/ProductDetail/Taiwan-Semiconductor/BZX85C12-R0G?qs=70cth9uAySd1on94GT9WfA%3D%3D https://www.mouser.com/ProductDetail/Vishay-Semiconductors/BZX55C12-TR?qs=WLTup5mM6hjdDCpNA5XDEA%3D%3D https://www.mouser.com/ProductDetail/ON-Semiconductor-Fairchild/BZX85C12?qs=SSucg2PyLi6g04ODt5vpWQ%3D%3D https://www.mouser.com/ProductDetail/Nexperia/BZX79-C12113?qs=me8TqzrmIYXUXVlyPuzVvg%3D%3D is brand the only thing that's different? am I just looking for C12? Any other parts I should replace while I'm at it that maybe a possible cause? Components are cheap and I'm already paying the shipping and handling. Thanks everyone for your help. |
| wraper:
You partially can test zener diode with multimeter (in diode mode) just as usual diode. It should conduct in one direction. However to measure clamping voltage, you need to connect in to power supply through current limiting resistor and measure voltage. As it seems to be 12V zener, you will need power supply with higher output voltage, somewhere in a range of 15-30V will do the job. As of replacement, any small 12V zener diode should do the job. |
| wraper:
--- Quote from: N19htmare on August 30, 2020, 05:10:06 am ---I measured the resistors out of the amp and they corralate their reading with the line markings I checked online, I'm getting new ones anyways. --- End quote --- Replacing non faulty resistors is pointless, not to say you can make some mistake when blanket replacing them. |
| N19htmare:
Alright, little update. Not a good one. I replaced the Diode, all the resistors, and the opamp that you see in that corner along with the two capacitors in that area. SAME PROBLEM! I still have to apply heat which leads me to believe that the board itself could be the cause. They may be a micro disconnect somewhere in the traces and small amount of heat is enough to expand it and connect it until it cools down again. I'm just guessing at this point. I'm baffled. |
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